Combination Oxygenator and Arterial Filter Device for Treating Blood in an Extracorporeal Blood Circuit

ABSTRACT

A combination oxygenator and arterial filter device for treating blood in an extracorporeal circuit includes a housing, an oxygenator, and a depth filter. The oxygenator includes a hollow fiber bundle forming an oxygenator exterior face. The depth filter is disposed (e.g., wound) directly over the exterior face, and includes a plurality of filaments arranged to define filter layers of level wound filaments. A first layer directly abuts the oxygenator exterior face. The oxygenator bundle differs from the depth filter in terms of: fiber and filament materials, construction of the fibers and filaments, and/or minimum gap spacings between axially adjacent ones of the fibers and the filaments. An oxygenator with integrated arterial filtering capability is provided that minimally impacts the extracorporeal blood circuit prime volume.

BACKGROUND

The present disclosure relates to extracorporeal blood circuits,systems, and methods of use. More particularly, it relates to devicesfor oxygenating and filtering blood in an extracorporeal blood circuit,and methods of making such devices.

An extracorporeal blood circuit is commonly used during cardiopulmonarybypass to withdraw blood from the venous portion of the patient'scirculation system (via a venous cannula) and return the blood to thearterial portion (via an arterial cannula). The extracorporeal bloodcircuit generally includes a venous drainage or return line, a venousblood reservoir, a blood pump, an oxygenator, an arterial filter, andblood transporting tubing, ports, and connection pieces interconnectingthe components. As shown in FIG. 1, some prior art extracorporeal bloodcircuits drain venous blood from patient 10 via a venous return line 12.Cardiotomy blood and surgical field debris are aspirated from thepatient 10 by a suction device 16 that is pumped by a cardiotomy pump 18into a cardiotomy reservoir 20. Venous blood from the venous return line12, as well as de-foamed and filtered cardiotomy blood from thecardiotomy reservoir 20, are discharged into a venous blood reservoir22. Air entrapped in the venous blood rises to the surface of the bloodin the venous blood reservoir 22 and is vented to atmosphere through apurge line 24. A venous blood pump 26 draws blood from the venous bloodreservoir 22 and pumps it through an oxygenator 28 and an arterial bloodfilter 29. An arterial line 14 returns the oxygenated and filtered bloodback to the patient's arterial system via an arterial cannula (notshown) coupled to the arterial line 14.

The oxygenator component of the extracorporeal blood circuit is wellknown. In general terms, the oxygenator takes over, either partially orcompletely, the normal gas exchange function of the patient's lungs. Inoxygenators that employ a microporous membrane, blood is taken from thepatient and is circulated through the oxygenator on one side of themembrane. Concurrently, an oxygenating gas is passed through theoxygenator on the other side of the membrane. Carbon dioxide diffusesfrom the blood across the microporous membrane into the passing streamof oxygenating gas; at the same time, oxygen diffuses from theoxygenating gas across the membrane into the blood. The circulatingblood, having thereby been reduced in carbon dioxide content andenriched in oxygen, is returned to the patient. One popular type ofmembrane oxygenator is referred to as a hollow fiber oxygenator, and isillustrated generally in U.S. Pat. No. 4,239,729. A hollow fiberoxygenator employs a large plurality (typically tens of thousands) ofmicroporous or semipermeable hollow fibers disposed within a housing.These hollow fibers are sealed in end walls of the housing that are thenfitted with skirted end caps. One end cap is fitted with an inlet, theother end cap is fitted with an outlet. A peripheral wall of the housinghas an inlet located interiorly of one of the end walls and an outletlocated interiorly of the other end wall. The oxygenating gas enters thedevice through the inlet, passes through the lumens of the hollowfibers, and exits the device through the outlet. It will be understoodthat carbon dioxide diffuses from the blood flowing over the outersurfaces of the hollow fibers through the fiber walls and into thestream of oxygenating gas. At the same time, oxygen from the oxygenatinggas flowing through the lumens of the hollow fibers diffuses through thefiber walls and into the blood flowing about the fibers to oxygenate theblood.

A well-accepted technique for forming a hollow fiber oxygenator is tospirally wind ribbons of the fibers about an internal supporting core,as described for example in U.S. Pat. No. 4,975,247. Blood flow throughthe resultant annular “bundle” of fibers can be in various directionssuch as radially outward, axial, circumferential, etc. With radiallyoutward flow designs, U.S. Pat. No. 5,462,619 describes an improvedwinding technique that provides desired pressure drops and minimalclotting risks by a graduated packing fraction. An oxygenator productavailable from Medtronic, Inc., under the trade name Affinity® NTOxygenator, is one example of a spirally wound hollow fiber oxygenatorwith graduated packing fraction.

For purposes of this disclosure, packing fraction is defined to mean thefraction of a unit volume of bundle space occupied by fibers (orfilaments). The packing fraction may be determined in ways known in theart, including the convenient method of measuring the interstitial spacebetween fibers (or filaments) by weight gain when a unit volume isprimed with a known liquid. Packing fraction at a particular region orzone located radially outward may be determined by stopping thecorresponding winding process at the radially inner radial boundary ofthe region or zone and determining the packing fraction at that stage,and then continuing the winding process to the outer radial boundary ofthe region or zone and determining the packing fraction at that stage.Computations known in the art will determine the packing fraction of theregion or zone using the prior two values.

Arterial filters are also well known, and can take various formsappropriate for air handling and blood filtration. In general terms, theconventional arterial filter device includes one or more screen-typefilters within a filter housing that combine to capture and removeparticulate (e.g., emboli) on the order of about 20-40 microns andlarger, as well as to trap gaseous microemboli larger than a certainsize to prevent the emboli from reaching the patient. These emboli cancause significant harm to the patient by plugging small arteries,arterioles, and or capillaries, preventing adequate blood flow to smallor large areas of tissue or organs. Examples of known arterial bloodfilters are described in U.S. Pat. Nos. 5,651,765 and 5,782,791.Arterial blood filters are also available from Medtronic, Inc. under thetrade name Affinity® Arterial Filter.

Conventionally, the arterial filter device is fluidly connected withinthe extracorporeal circuit downstream (or upstream) of the oxygenatordevice by tubing. While implementation of the separate oxygenator andarterial filter devices as part of an extracorporeal blood circuit iswell accepted, certain concerns arise. An arterial filter typically adds200 ml (or more) of prime volume to the extracorporeal blood circuit;this added prime volume is undesirable as it can lead to increasedhemodilution of the patient. As a point of reference, the volume ofblood and/or prime solution liquid that is pumped into theextracorporeal blood circuit to “prime” the circuit is referred to asthe “prime volume”. Typically, the extracorporeal blood circuit is firstflushed with CO₂ prior to priming. The priming flushes out anyextraneous CO₂ gas from the extracorporeal blood circuit prior to theintroduction of the blood. The larger the prime volume, the greater theamount of prime solution present in the extracorporeal blood circuitthat mixes with the patient's blood. The mixing of the blood and primesolution causes hemodilution that is disadvantageous and undesirablebecause the relative concentration of red blood cells must be maintainedduring the surgical procedure in order to minimize adverse effects tothe patient. It is therefore desirable to minimize the extracorporealblood circuit's prime volume (and thus the required volume of primesolution).

In light of the above, a need exists for an extracorporeal blood circuitdevice that provides oxygenation and arterial filtering properties atleast commensurate with conventional oxygenator and arterial filtercomponents, yet minimizes the overall impact on the prime volume of theextracorporeal blood circuit.

SUMMARY

Some aspects in accordance with principles of the present disclosurerelate to a combination oxygenator and arterial filter device fortreating blood in an extracorporeal blood circuit. The device includes ahousing, an oxygenator, and a depth filter. The oxygenator is maintainedwithin the housing and includes a plurality of hollow fibers helicallywound about an internal core to define an oxygenator bundle forming anoxygenator exterior face. The depth filter is disposed directly over theoxygenator exterior face, and includes a plurality of filaments arrangedto define first and second filter layers of level wound filaments (e.g.,level cross-wound filaments). The first filter layer directly abuts theoxygenator exterior face, and the second filter layer directly abuttingthe first layer opposite the oxygenator exterior face. The oxygenatorbundle and depth filter can both be annular, defining a common centralaxis. Regardless, a structure of the oxygenator bundle differs from astructure of the depth filter by at least one characteristic selectedfrom the group consisting of: materials of the fibers and the filaments,construction of the fibers and filaments, and/or minimum gap spacingsbetween adjacent, axially aligned ones of the fibers and minimum gapspacings between adjacent, axially aligned ones of the filaments. Insome embodiments, an outer diameter of the depth filter filaments isless than an outer diameter of the oxygenator bundle fibers. In otherembodiments, some or all of the depth filter filaments are solid. In yetother embodiments, the oxygenator bundle fibers are formed of a firstmaterial and the depth filter filaments are formed of a second materialdiffering from the first material. In yet other embodiments, a minimumgap spacing between axially adjacent filaments of the first filter layeris less than a minimum gap spacing between axially adjacent fibers ofthe oxygenator bundle. The filaments of the depth filter can be woundover the oxygenator bundle. Alternatively, the filaments can be knittedinto a mat or formed into a double weft tape applied over the oxygenatorexterior face. With any of these constructions, an oxygenator withintegrated arterial filter capability is provided having reduced foreignsurface area and reduced impact on the prime volume of the correspondingextracorporeal blood circuit (e.g., on the order of 25 ml or less) ascompared to conventional arterial filter devices provided physicallyapart from the oxygenator.

Yet other aspects in accordance with principles of the presentdisclosure relate to an extracorporeal blood circuit including a venousline, an arterial line, and a combination oxygenator and arterial filterdevice. The combination oxygenator and arterial filter device forms aninlet side and an outlet side. The inlet side is fluidly connected tothe venous line, that in turn is arranged to receive blood from apatient (e.g., via a pump). Conversely, the outlet side is fluidlyconnected to the arterial line that in turn is located to deliver bloodto the patient. The combined oxygenator and arterial filter deviceincludes the oxygenator bundle and depth filter as described above. Insome embodiments, the extracorporeal blood circuit is characterized bythe absence of an additional arterial filter between the combinationoxygenator and arterial filter device and the arterial line.

Yet other aspects in accordance with principles of the presentdisclosure relate to a method of making a combination oxygenator andarterial filter device for treating blood in an extracorporeal bloodcircuit. The method includes helically winding a plurality of hollowsemipermable fibers about an internal core to define an oxygenatorbundle forming an oxygenator exterior face. A depth filter is applieddirectly over and in contact with the oxygenator exterior face, with thedepth filter including a plurality of filaments arranged to defineradially-arranged, first and second filter layers of level woundfilaments. The first filter layer abuts the oxygenator exterior face,whereas the second filter layer abuts the first filter layer oppositethe oxygenator exterior face. Finally, a structure of the oxygenatorbundle differs from a structure of the depth filter by at least one of:the materials of the oxygenator bundle fibers and the depth filterfilaments, construction of the oxygenator bundle fibers and the depthfilter filaments, and minimum gap spacings between adjacent, axiallyaligned ones of the depth filter fibers and minimum gap spacings betweenaxially adjacent ones of the depth filter filaments. In someembodiments, the step of applying the depth filter includes helicallywinding the plurality of filaments over the oxygenator bundle. Inrelated embodiments, the plurality of hollow fibers are helically woundabout the internal core by threading a guide tube of a winding apparatuswith the hollow fibers and rotating the internal core relative to theguide tube. With these embodiments, subsequent helical winding theplurality of filaments includes removing the hollow fibers from theguide tube, threading at least some of the filaments into the guidetube, and then rotating the internal core relative to the fiber guidetube so as to apply the filaments onto the oxygenator bundle and formthe depth filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a prior art extracorporeal bloodcircuit including separated oxygenator and arterial filter devices;

FIG. 2A is a cross-sectional view of a combination oxygenator andarterial filter device in accordance with principles of the presentdisclosure, depicting the device vertically oriented as it would be inuse;

FIG. 2B is a cross-sectional view of another combination oxygenator andarterial filter device in accordance with principles of the presentdisclosure;

FIG. 2C is a cross-sectional view of another combination oxygenator andarterial filter device in accordance with principles of the presentdisclosure;

FIG. 3A is a perspective, exploded view of oxygenator bundle and depthfilter components of the devices of FIGS. 2A-2C;

FIG. 3B is a simplified, greatly magnified top plan view of a portion ofthe oxygenator bundle of FIG. 3A;

FIG. 3C is a cross-sectional, greatly magnified view of a portion of theoxygenator bundle of FIG. 3A;

FIG. 4A is a perspective, greatly magnified view of a portion of thedevices of FIGS. 2A-2C, illustrating the depth filter of FIG. 3A appliedto the oxygenator bundle;

FIG. 4B is a cross-sectional, greatly magnified view of a portion of thedepth filter of FIG. 4A;

FIG. 5 is a simplified side view of a winding apparatus applying thedepth filter of FIG. 3A to the oxygenator bundle of FIG. 3A inaccordance with principles of the present disclosure;

FIG. 6A is a simplified schematic illustration of another embodimentdepth filter useful with the devices of FIGS. 2A-2C;

FIG. 6B is an enlarged view of a portion of the depth filter of FIG. 6A;

FIG. 7 is a simplified schematic illustration of a double weft tapeuseful as the depth filter of the devices of FIGS. 2A-2C;

FIG. 8 is a cross-sectional, greatly magnified view of an alternativedepth filter useful with the devices of FIGS. 2A-2C; and

FIG. 9 is a schematic diagram of an extracorporeal blood circuitincorporating the devices of FIGS. 2A-2C in accordance with principlesof the present disclosure.

DETAILED DESCRIPTION

One embodiment of a combination blood oxygenator and arterial filterdevice 30 in accordance with principles of the present disclosure isshown in FIG. 2A. The device 30 includes a housing 32, an oxygenator 34(referenced generally) and an arterial depth filter 36 (referencedgenerally). Details on the various components are provided below. Ingeneral terms, however, the oxygenator 34 includes an internal core 38about which an oxygenator bundle 40 is formed. The depth filter 36 isdisposed directly over the oxygenator bundle 40, with the so-constructedoxygenator 34 and depth filter 36 contained within the housing 32. Ablood flow path is defined by the housing 32, directing blood flowradially through the oxygenator bundle 40 and then the depth filter 36,with the oxygenator bundle 40 facilitating oxygenation of the suppliedvenous blood, and the depth filter 36 removing gaseous and particulatemicroemboli. The device 30 is thus amenable for insertion within anextracorporeal blood circuit as described below, providing necessaryoxygenation and filtration capabilities with minimal overall impact onthe extracorporeal circuit's prime volume.

The housing 32 can assume various forms, and generally includes ordefines an outer wall 50, a gas header or cap 52, and a bottom header orcap 54. The outer wall 50 is sized to contain the oxygenator 34 and thedepth filter 36, and can be generally cylindrical. At a base region 56,an optional annular eccentric relieved area 58 forms, or is fluidlyconnected to, an outlet manifold 60 having a blood outlet 62. Otheroptional outlets or ports, such as sample or recirculation ports 64, canbe provided by the manifold 60 or may be suitably located elsewherealong the outer wall 50.

The gas header 52 is configured for assembly to the outer wall 50, andincludes or defines a gas inlet 66. Similarly, the bottom header 54 isconfigured for assembly to the outer wall 50 opposite the gas header 52,and can form or include a gas outlet 68. The bottom header 54 alsoincludes or defines a blood entrance or inlet 70 for directing a bloodflow into the device 30.

The device 30, at the bottom header 54, can optionally be provided with,or carry, a suitable heat exchanger 72. A fluid type heat exchanger 72is depicted with a heat exchange fluid inlet 74 and a heat exchangefluid outlet 76, but other suitable heat exchange devices can beincorporated with the device 30, for example an electrical heating andcooling device might be used. In other embodiments, the heat exchanger72 is omitted. For example, FIG. 2B illustrates an alternative device30′ in accordance with principles of the present disclosure andincluding the oxygenator bundle 40 and the arterial depth filter 36within a housing 32′. The device 30′ does not include a heat exchanger.Conversely, FIG. 2C illustrates another device 30″ in accordance withthe principles of the present disclosure and including the oxygenatorbundle 40 and the arterial depth filter 36 within a housing 32″.Further, a bundled heat exchanger 85 is disposed between the oxygenatorbundle 40 and the core 38.

Returning to FIG. 2A and as mentioned above, the oxygenator 34 includesthe internal core 38 and the oxygenator bundle 40. The internal core 38is a generally cylindrical, hollow body, and is configured for windingof (and supporting) the oxygenator bundle 40 about an outer surfacethereof. The internal core 38 can optionally incorporate variousfeatures (e.g., ribs, flanges, recessed regions, etc.) that promoterobust assembly with the oxygenator bundle 40. Regardless, the internalcore 38 forms a central passage 78 that is fluidly open to the bloodinlet 70 at a first end 80. A chamber 82 is formed adjacent a second end84 of the core 38, and is fluidly open to an exterior of the internalcore 38 by one or more windows (not shown) that dictate a radiallyoutward blood flow path from the passage 78 as reflected by arrows inFIG. 2A.

The oxygenator bundle 40 is an annular bundle of helically-wound,microporous hollow fibers (drawn generally in FIG. 2A, but identified ingreater detail below with reference to FIGS. 3A-3C) positioned along theinternal core 38. The top and bottom ends of the oxygenator bundle 40are embedded in solidified potting compositions 86, 88 at top and bottomends, respectively, of the housing 32. The fiber lumens communicate withthe outer surface of the upper and lower potted compositions 86, 88,respectively. An oxygenating gas introduced via the gas inlet 66 flowsinto the gas header 52, through the lumens of the hollow fibers, down tothe opposite ends of the hollow fibers at the lower potted region 88,and into the gas outlet passage 68.

It should be understood that the potting process referred to hereinabove is a well known fiber potting process in which a potting material(e.g., polyurethane) is introduced by centrifuging and reacted in situ.Other appropriate potting materials may be used. Suitable sealants andgaskets may be used at joints in the housing 32, such as the jointsbetween the top and bottom headers 52, 54 and the outer wall 50. Anysuitable microporous fiber may be used in the oxygenator bundle 40; forexample, a suitable fiber is the microporous polypropylene fiberavailable under the trade name CELGARD™ X30 (outer diameter on the orderof 200-300 microns) from Membrana of Charlotte, N.C.

The hollow fiber oxygenator bundle 40 extends radially outward relativeto a central axis C of the internal core 38. The fibers can include afirst plurality of fibers positioned (e.g., wound) helically around theinternal core 38 in a first direction from the first end 80 to thesecond end 84 of the internal core 38, and a second plurality of fiberspositioned helically around the internal core 38 in a second directionopposite the first direction, and thus from the second end 84 to thefirst end 80. Various acceptable methods of winding the microporousfibers about the internal core 38 to generate the oxygenator bundle 40are described in U.S. Pat. Nos. 4,975,247 and 5,462,619, the entireteachings of both of which are incorporated herein by reference. Forexample, as described in the '619 Patent, the oxygenator bundle 40 canbe wound to define a graduated packing fraction that increases from aninside radius of the oxygenator bundle 40 to the outside radius.

Regardless of the packing fraction properties of the oxygenator bundle40, an oxygenator exterior face 100 is provided, as shown in FIG. 3A.The oxygenator exterior face 100 is defined as the terminal face of theoxygenator bundle 40 opposite the internal core 38 (omitted from theview of FIG. 3A for ease of explanation, but a location of whichrelative to the oxygenator bundle 40 being generally indicated). Theoxygenator exterior face 100 is generally annular, and is comprised of aseries of axially or longitudinally adjacent windings of the hollowfibers 102 (a thickness or diameter of which is exaggerated in FIG. 3Afor ease of explanation). Commensurate with the above descriptions,individual ones of the hollow fibers 102 may be arranged in differingwind directions along the oxygenator exterior face 100. Further, in someembodiments, selected groupings of the hollow fibers 102 may becollectively cross-wound in identical directions as a fiber ribbon(e.g., as described in the '619 Patent, six continuous hollow fibers arecollectively cross-wound as a discernable ribbon). As such, not all ofthe fibers 102 along the oxygenator exterior face 100 may be preciselyaxially aligned. For example, FIG. 3B depicts a ribbon 103 of the fibers102 being collectively cross-wound, with exposed segments 103 a, 103 b,103 c of the wound fiber ribbon 103 each forming a portion of theoxygenator exterior face 100. However, and as reflected in FIG. 3C, aminimum gap spacing 104 is established between axially adjacent ones ofthe fibers 102, with the minimum gap spacing 104 being in the range of20-70 microns in some embodiments, in the range of 30-60 microns inother embodiments, and on the order of 38 microns in other embodiments.

Returning to FIG. 3A, the depth filter 36 is constructed to be directlyapplied or formed over the oxygenator bundle 40 as described below, andis generally characterized as a radially outward extension from theoxygenator exterior face 100. In particular, the depth filter 36includes a plurality of filaments 110 (referenced generally) arrangedover the oxygenator exterior face 100. The filaments 110 can be madefrom a plastic resin such as polyester, polypropylene, polyethylene,etc., and can be solid filaments and/or microporous hollow filaments.The filaments 110 may or may not be identical in terms of material,structure, or size, but in some embodiments a maximum outer diameter ofthe filaments 110 is not greater than about 200 microns; in otherembodiments not greater than 150 microns. In yet other embodiments, anouter diameter of the filaments 110 is in the range of 40-50 microns.

Regardless of an exact construction and/or materials of the filaments110, the filaments 110 are arranged over the oxygenator exterior face100 so as to define level cross-wound filter layers as shown in FIG. 4A(the oxygenator bundle 40 and the oxygenator exterior face 100 shownschematically in FIG. 4A for ease of illustration). In FIG. 4B, thedepth filter 36 has at least a first filter layer 120 of level woundfilaments optionally a second filter layer 122 of level wound filaments,and possibly additional filter layers (not shown) of level woundfilaments on the second layer 122. The layers 120, 122 are annular,arranged about the central axis C described above, with various ones ofthe filaments 110 extending spirally around the central axis C. In someembodiments, the filaments 110 extend in differing directions along eachof the layers 120, 122 such that each of the layers 120, 122 is composedof level cross-wound filaments. Alternatively, the filaments in one orboth of the layers 120, 122 can be level wound without cross-winding.With the construction of FIGS. 4A and 4B, the layers 120, 122 can becharacterized as cross-level wound or plan level composite wound filterlayers 120, 122.

A minimum gap spacing 124 is established between axially orlongitudinally adjacent ones of the filaments 110 within each of thefirst and second layers 120, 122. The phrases “axially adjacent” and“longitudinally adjacent” as used in this disclosure are in reference totwo filaments (or fibers) immediately above or below one another andhaving aligned center points that intersect in a plane parallel to thecentral axis C. Thus, relative to the first filter layer 120, axially orlongitudinally adjacent filaments 110 a, 110 b establish the minimum gapspacing identified at 124 a; similarly, the filaments 110 c, 110 d ofthe second filter layer 122 establish the minimum gap spacing identifiedat 124 b. It will be understood that with certain manufacturingtechniques envisioned by the present disclosure, in some regions of thedepth filter 36, a larger gap may exist between axially adjacentfilaments 110. By minimizing a size of the minimum gap spacings 124(e.g., on the order of 40 microns), radial blood flow through the filterlayers 120, 122 provides enhanced filtration efficiency for a given sizeof microemboli. Although the depth filter 36 has been described ashaving two of the filter layers 120, 122, in other embodiments, three orfour or more of the layers of level wound filaments can be formed by thefilaments 110, with each successive layer being radially outward of theprevious layer. Regardless, and as reflected in FIG. 4B, the firstfilter layer 120 is formed directly on the oxygenator exterior face 100such that the filaments 110 of the first layer 120 physically contactthe fibers 102 of the oxygenator exterior face 100.

In some embodiments, the filaments 110 are applied to the oxygenatorexterior face 100 via a winding operation. The filament winding processmay be conveniently performed on an apparatus of the type illustratedschematically in FIG. 5, that optionally may also be employed forwinding the oxygenator bundle 40 onto the internal core 38. In generalterms, the filament winding apparatus comprises a rotating mountingmember 130 and a guide head 132. The rotating mounting member 130rotatably maintains the internal core 38 (referenced generally), andthus the previously-formed oxygenator bundle 40 (the exterior face 100of which is partially visible and drawn schematically in FIG. 5 for easeof explanation). The guide head 132 is arranged to travel reciprocallyas illustrated by a double-headed arrow line A in FIG. 5 with respect toa longitudinal axis B of the mounting member 130 (i.e., the line oftravel A of the guide 132 is parallel to the axis of rotation B of themounting member 130).

As described, for example, in U.S. Pat. No. 4,975,247, the guide head132 maintains a number of fiber guides (e.g., tubes, holes, pins, etc.)through which the filaments 110 are threaded as they enter the guidehead 132 from a supply container (not shown). Upstanding ribs, grooves,guide pins, tubes, etc., may be used to space the filaments 110 at theguide head 132. Commercially available winding apparatus are availablefor wrapping the continuous filaments 110 on the oxygenator bundle 40.For example, Entec of Salt Lake City, Utah offers a winding apparatuswith electronic gearing for varying the rotational speed of the mountingmember 130 and the traverse speed of the guide head 132 during winding.The internal core 38 of the oxygenator 34 is mounted on the mountingmember 130, with central axis C of the oxygenator 34 thus aligned withthe axis of rotation B. The guide head 132 is then positioned at theleft hand side (as viewed in FIG. 5) of the oxygenator bundle 40. Aribbon 140 of continuous filaments 110 (e.g., six of the filaments 110)is threaded through the fiber guides of the guide head 132. The leadingend of the filament ribbon 140 is affixed to the oxygenator exteriorface 100 extended at the far left end thereof. Rotation of the mountingmember 130 is begun in the direction indicated by arrow R in FIG. 5.Motion of the guide head 132 is synchronized with rotation of themounting member 130, and automatically travels axially of the oxygenatorbundle 40 as the mounting member 130 rotates. It will be recognized bythose skilled in the art that the guide head 132 travels axially a fixeddistance for each revolution of the mounting member 130.

The guide head 132 travels from the first end 80 (left hand side of FIG.5) of the internal core 38 to the second end 84 (right hand side of FIG.5) where it decelerates. After decelerating, the guide head 132 reversesdirection, accelerates and travels back to its starting position. Afterdecelerating again and reversing direction, the guide head 132 beginsits travel cycle anew. Alternatively, the guide head 132 may stop anddwell at the end points of the traverse. The reciprocal travel for theguide head 132 and the concurrent rotation of the mounting member 130 onwhich the oxygenator 34 has been mounted is continued until a depthfilter filament bundle of desired diameter has been wound onto theoxygenator bundle 40, with the back-and-forth cycling of the guide head132/ribbon 140 creating the level cross-wound layers described above.

As explained more fully at column 10, line 23 through column 11, line 62of the '247 Patent, in the left-to-right travel of the guide head 132,the filament ribbon 140 is wound spirally around the oxygenated bundle40, and the individual filaments 110 in the ribbon 140 are laid down incontact with the oxygenator exterior face 100. In the subsequent secondtraverse (right-to-left in FIG. 5) of the guide head 132, the filamentribbon 140 continues to be spirally wound onto the oxygenator bundle 40.Portions of the filaments 110 laid down during the second traverse ofthe guide head 132 contact previously-applied filaments 110 at certaincrossover points. Except for these crossover points at which there isfilament-to-filament contact with the filaments 110 laid down during thefirst traverse of the guide head 132, the filaments 110 laid down duringthe second traverse of the guide head 132 come into direct contact withthe oxygenator exterior face 100. In the winding procedure beingdiscussed, the oxygenator exterior face 100 is covered, except for thegap spacing 124 (FIG. 4B) between adjacent filaments 110. Filaments ofthe ribbon 140 laid down at a later traverse of the guide head 132 willbe in radial registry with the filaments 110 laid down during an earliertraverse of the guide head 132 as described in the '247 Patent.

With embodiments in which the depth filter 36 (FIG. 3A) is formed bywinding the filaments 110 onto the oxygenator bundle 40 as describedabove, the ratio of the mounting member 130 rotational speed relative tothe traverse motion of the guide head 132 can be adjusted incrementallyduring the winding operation, thereby adjusting a wind angle of thefilament ribbon 140. With this approach, a packing fraction of thefilaments 110 along radial a thickness of the depth filter 36 isaffected to provide a radially increasing packing fraction.Alternatively, or in addition, a tension of the filaments 110 can beregulated during the winding process. In particular, an optional roller142 can be employed to apply tension to the ribbon 140. The roller 142may rotate in response to the fiber ribbon 140 moving against it or maybe driven so that its rotation matches the speed of the ribbon 140.Where the tension of the filaments 110 is increased during winding, anincreasing packing fraction is obtained in a radially outward direction;thus, a force of the roller 142 against the filaments 110 can beincreased to increase the resultant packing fraction. As a furtheralternative, a spacing between two (or more) filaments beingsimultaneously wound may be decreased during the winding operation,either incrementally or continuously, to increase packing fractions in aradially outward direction as described, for example, in the '619Patent. In other embodiments, the packing fraction can be constant ordecreasing in the radially outward direction. In yet other embodiments,the filaments 110 can be wound on a more individual basis (e.g., thecontinuous ribbon 140 technique described above need not be employed).

In some embodiments, the winding apparatus described above is employedto form the oxygenator bundle 40 about the internal core 38. Forexample, the internal core 38 is initially assembled to the rotatingmounting member 130, and the guide head 132 employed to apply a ribbonof the fibers 102 (FIG. 3B) onto the internal core 38. Followingformation of the oxygenator bundle 40, the fibers 102 are removed fromthe fiber guides (e.g., withdrawn from the tubes carried by the guidehead 132), and replaced with the filaments 110 as described above. Thus,the depth filter 36 can optionally be formed over the oxygenator bundle40 immediately after applying the fibers 102 to the internal core 38 andwithout removing the so-formed oxygenator 34 from the winding apparatus.

While the depth filter 36 has been described as being wound directlyonto the oxygenator bundle 40, other constructions are also acceptable.For example, the depth filter 36 can be formed or provided apart fromthe oxygenator bundle 40 as a filament mat, comprising two or moreplies. U.S. Pat. No. 4,940,617 describes two-ply (or multi-ply) matshaving parallel fibers interconnected by cross-stitching where thefibers in one ply form an angle relative to the fibers in an adjacentply or layer. The '617 Patent also shows the construction of bundles bywinding such mats onto a core. Column 3, line 26 through column 14, line67, including the figures referenced therein, contain the disclosure ofsuch mats and bundles and the teachings of which are incorporated hereinby reference, it being understood that the filaments 110 of the presentdisclosure could be used as the fibers of the '617 Patent. In generalterms, and as shown in FIG. 6A, a filament mat 150 useful as the depthfilter 36 (FIG. 2A) in accordance with the present disclosure consistsof the filaments 110 combined into groups or plies 152, 154 by specialdisposition of inserted transverse fibers 156 or the like. In someconstructions, and as shown in FIG. 6B for one of the plies 152, aninterval between some of the filaments 110 can vary from the intervalbetween others of the filaments 110. A gap 158, formed by thisdisposition of filament ends, between the filament groups, permitsbetter penetration of the medium flowing around the filaments 110 in theresultant mat 150. Returning to FIG. 6A, the additional transversefibers 154 or the like, and inserted in the middle of the filaments 110,are disposed such that they hold the filaments 110 at a regular,essentially identical interval to each other. Regardless of an exactconstruction, and with cross-reference to FIG. 3A, the mat 150 is rolledor wrapped about the exterior face 100 of the oxygenator bundle 40, andforms the depth filter 36 having at least the first and second levelcross-wound filter layers as described above.

In yet another acceptable embodiment, the depth filter 36 is provided asa woven filament double weft tape as described, for example, in U.S.Pat. No. 5,141,031, the entire teachings of which are incorporatedherein by reference. In general terms, and as shown in FIG. 7, a doubleweft tape 160 including a plurality of the filaments 110 are embedded inhead plates 162. Typically, the filament ends are embedded by spinningthem into a curable potting compound. Regardless, the double weft tape160 provides various filament tapes arranged in layers around a core 164(e.g., the oxygenator bundle 40 (FIG. 3A)) in such a way that thefilaments 110 of adjacent layers form layers with an angle α that is notgreater than 30° in some embodiments. The double weft tape 160 is akinto the two-ply mat 150 (FIG. 6A) described above, but typically exhibitsa more narrow width. The tape 160 can be wrapped or wound about theoxygenator exterior face 100 (FIG. 3A) to form the depth filter 36 asdescribed above.

Returning to FIGS. 4A and 4B, regardless of an exact construction of thedepth filter 36 and corresponding assembly to the oxygenator bundle 40,the first and second filter layers 120, 122 of level wound filamentsestablish a tortuous radial flow path for blood flow through the depthfilter 36. Thus, the depth filter 36 is markedly different from thescreen or mesh construction associated with conventional arterialfilters. In other words, the radial flow paths (i.e., gap spacings)between the filaments 110 of the first layer 120 are not radiallyaligned with those of the second layer 122, thus defining a “depth” tothe depth filter 36. In contrast, with screen or mesh filters, the flowpath spacing are radially open or “linear” through a thickness of thematerial. The minimum gap spacings 124 between the filaments 110 and thenumber of filter layers are two of the factors that determine theefficiency of the depth filter 36 for a given size of microemboli.Further, the gap spacings 124 between the filaments 110, the outerdiameter of the filaments 110, and the crossing angle of the filaments110 determine a percentage of open area of the depth filter 36. Byemploying reduced outer diameter filaments (as compared to an outerdiameter of the fibers 102 of the oxygenator bundle 40), the minimum gapspacings 124 between the filaments 110 can be reduced (as compared tothe minimum gap spacings 104 (FIG. 3C) between the fibers 102 of theoxygenator bundle 40) without increasing the shear to which the bloodflow is exposed. In some embodiments, the depth filter 36 is configuredto filter or remove microemboli as understood in the art, for exampleparticulate microemboli as small as 15 micron, and gaseous microemboli(i.e., bubbles) on the order of 250 microns or less. With embodiments inwhich the filaments 110 are microporous gas conducting hollow filaments,a pressure drop across the depth filter 36 will provide a favorablepressure gradient to drive gaseous microemboli through the pores andinto the lumens of the filaments 110. The gas from the so-capturedgaseous microemboli can be vented to the atmosphere through the gasoutlet 68 (FIG. 2A) associated with the oxygenator bundle 40, or to aseparate manifold.

While the depth filter 36 has been described as utilizing relativelyuniform filaments across a radial thickness of the depth filter 36, inother constructions, variations in the filaments 110 can beincorporated. For example, FIG. 8, illustrates, in simplified form, aportion of an alternative depth filter 36′ in accordance with thepresent disclosure. The depth filter 36′ is akin to previousembodiments, and includes a plurality of level wound filaments combiningto define two or more filter layers 180. As a point of reference, theinner most layer 180 a is placed in direct physical contact with theexterior face 100 of the oxygenator bundle 40 (illustratedschematically) upon final assembly. Various differences are incorporatedinto one or more of the layers 180 to create two (or more) filteringzones 182, 184 exhibiting different filtration characteristics orproperties. For example, filaments 186 of the first zone 182 can behollow, whereas filaments 188 of the second zone 184 are solid (orvice-versa); as a result, the first zone 182 more readily filters orremoves gaseous microemboli, whereas the second zone 184 more activelyfilters particulate microemboli. Other differences, such as filamentmaterials, minimum gap spacings, packing fraction, etc., canalternatively or additionally be incorporated in the zones 182, 184 toprovide desired dual functioning filtration.

Returning to FIG. 3A, although in certain respects the level cross-wovenlayers of the depth filter 36 are akin to the oxygenator bundle 40, oneor more structural differences exist between the depth filter 36 and theoxygenator bundle 40. In general terms, these differences are uniquelyselected to promote functioning of the oxygenator bundle 40 to oxygenate(and remove carbon dioxide from) blood flow, whereas the depth filter 36removes or filters gaseous and particulate microemboli. For example, insome embodiments, the plastic resin of the depth filter filaments 110differs from the plastic resin of the oxygenator bundle fibers 102(e.g., the depth filter filaments 110 are formed of polyester, polymethyl pentene, or silicone, whereas the oxygenator bundle fibers 102are formed of polypropylene). In other embodiments, the oxygenatorbundle fibers 102 are hollow, whereas at least some of the depth filterfilaments 110 are solid. In yet other embodiments, an outer diameter ofthe oxygenator bundle fibers 102 is greater than an outer diameter ofthe depth filter filaments 110 (e.g., the oxygenator bundle fibers 102have an average outer diameter in the range of 200-300 microns, whereasthe depth filter filaments 110 have an average outer diameter in therange of 100-250 microns). In yet other embodiments, the minimum gapspacing between axially adjacent ones of the oxygenator bundle fibers102 is less than the minimum gap spacing between axially adjacent onesof the depth filter filaments 110 (e.g., the minimum gap spacing betweenaxially adjacent ones of the oxygenator bundle fibers 102 is in therange of 75-150 microns, whereas the minimum gap spacing between axiallyadjacent ones of the depth filter filaments 110 is in the range of 40-75microns). In yet other embodiments, a packing fraction of the depthfilter 36 is higher than the packing fraction at the exterior face 100of the oxygenator bundle 40. Alternatively, or in addition, a wind angleassociated with the fibers 102 of the oxygenator bundle 40 differs fromthe wind angle associated with the filaments 110 of the depth filter 36.In some constructions, two or more of the above-described differencesare incorporated into the depth filter 36 and the oxygenator bundle 40.

The combination oxygenator and arterial filter device 30 can beincorporated into an extracorporeal blood circuit 200 as shown in FIG.9. In general terms, the extracorporeal blood circuit 200 can be akin toany extracorporeal blood circuit commonly employed, and generallyincludes the venous return line 12, the cardiotomy pump and reservoir20, the venous blood reservoir 22, and the arterial line 14 as describedabove. The combination oxygenator and arterial filter device 30 isfluidly connected to the venous line 12, for example via an inlet side202. An outlet side 204 of the device 30 is fluidly connected to thearterial line 14. A source of oxygenating gas 206 is fluidly connectedto the device 30, establishing an oxygenating gas flow path to thehollow fibers 102 (FIG. 3C) of the oxygenator bundle 40 (FIG. 3A). Insome embodiments, the oxygenating gas flow path is fluidly closedrelative to the depth filter filaments 110 (FIG. 3A). Additionalcomponents can be interposed within the circuit 200. However, inaccordance with embodiments of the present disclosure, the device 30provides necessary arterial filtration, such that a separate oradditional arterial filter is not included between the device 30 and thearterial line 14. As compared to conventional extracorporeal bloodcircuit configurations, then, an overall prime volume is reduced withuse of the device 30. The extracorporeal blood circuit 200 is thussimplified as one less component need be fluidly connected into thecircuit 200.

EXAMPLES

The following examples and comparative examples further describe thecombination oxygenator and arterial filter devices of the presentdisclosure. The examples are provided for exemplary purposes tofacilitate an understanding of the present disclosure, and should not beconstrued to limit the disclosure to the examples.

Example combination oxygenator and arterial filter devices (Examples1-6) were constructed by forming a depth filter directly over theoxygenator bundle of a commercially available oxygenator (an Affinity®NT Oxygenator available from Medtronic, Inc., of Minneapolis, Minn., thefibers of which were coated with a Trillium® Biosurface available fromBioInteractions, Ltd., UK). The integrated arterial depth filter wasformed by spiral or cross-winding filaments in predetermined fashions toestablish two or more filter layers of level cross-wound filaments,including a designated gap spacing between axially adjacent filaments.The filament outer diameter, number of filter layers, and gap spacingfor each of Examples 1-6 are set forth in the Table below.

The filtration efficiency of the combination oxygenator and arterialfilter devices of Examples 1-6 was tested by flowing a particle-ladenfluid through the device, and determining the percentage of particlescaptured or retained by the device. The particles were latexmicrospheres, and batches of differently-sized particles were employedwith separate tests for each sample. For each test, the differencebetween the number or weight of the particles introduced to the deviceand number or weight of particles captured by the device were recordedand used to determine filtration efficiency. The particle size for eachtest is shown in the Table below, along with the determined filtrationefficiency.

To evaluate the filtration efficiency performance of the examplecombination oxygenator and arterial filter devices, commerciallyavailable arterial filters and commercially available oxygenators weresubjected to the tests descried above, and the results recorded. Inparticular, Comparative Examples 1 and 2 were commercially availablearterial filters (Affinity® Arterial Filter (38 micron filament gap))coated with Trillium® Biosurface. Comparative Examples 3 and 4 werecommercially available arterial filters (Affinity® Arterial Filter)coated with Carmeda® Biosurface (available from Carmeda AB of Sweden).Comparative Examples 5 and 6 were commercially available oxygenators(Affinity® NT Oxygenator available from Medtronic, Inc., of Minneapolis,Minn.) coated with Carmeda® Biosurface. Comparative Examples 7 and 8were commercially available oxygenators (Affinity® NT Oxygenator) coatedwith Trillium® Biosurface. The test results are provided in the Tablebelow.

TABLE Filtration Efficiency Integrated Arterial Filter 20 μm 45 μm 65 μm90 μm Filament OD Gap # Crossing Sample particles particles particlesparticles (microns) (microns) Layers E1 34.9% 94.6% 99.1% 100.0% 200 582 E2 56.2% 98.8% 100.0% 100.0% 130 58 6 E3 57.9% 97.2% 99.9% 99.9% 13058 6 E4 41.4% 94.8% 99.4% 100.0% 200 58 2 E5 19.2% 95.4% 99.7% 99.9% 13058 2 E6 38.1% 92.8% 99.1% 100.0% 130 51/51 2 CE1 11.7% 100.0% N/A N/A NA38 NA CE2 35.0% 99.8% N/A N/A NA 38 NA CE3 37.8% 99.8% N/A N/A NA 38 NACE4 12.7% 100.0% N/A N/A NA 38 NA CE5 54.5% 95.9% 99.7% 100.0% NA NA NACE6 45.4% 94.6% 99.1% 99.2% NA NA NA CE7 41.2% 92.6% 99.1% 100.0% NA NANA CE8 17.6% 90.8% 98.9% 100.0% NA NA NA

The test results reveal that the combination oxygenator and arterialfilter devices of the present disclosure were highly beneficial infiltration efficiency as compared to separate, standalone oxygenator andarterial filter products. The combination devices of Examples E1-E6effectively replace the separate arterial filters (CE1-CE4) andoxygenators (CE5-CE8), and thus reduce an overall prime volume. Asshown, the combination sample devices exhibited equal or betterfiltration efficiency as compared to the individual arterial filters oroxygenators.

Although the present disclosure has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges can be made in form and detail without departing from the spiritand scope of the present disclosure.

1-21. (canceled)
 22. A method of making a combination oxygenator andarterial filter device for treating blood in an extracorporeal bloodcircuit, the method comprising: helically winding a plurality of hollowmicroporous fibers about an internal core to define an oxygenator bundleforming at an oxygenator exterior face; applying a depth filter directlyover the oxygenator exterior face, the depth filter including aplurality of filaments arranged to define a first filter layer of levelwound filaments directly abutting the oxygenator exterior face and asecond filter layer of level wound filaments directly abutting the firstfilter layer opposite the oxygenator exterior face; wherein a structureof the oxygenator bundle differs from a structure of the depth filter byat least one characteristic selected from the group consisting of:materials of the fibers and filaments, construction of the fibers andthe filaments, and minimum gap spacings between axially adjacent ones ofthe fibers and axially adjacent ones of the filaments; and disposing theoxygenator bundle and the depth filter within a housing.
 23. The methodof claim 22, wherein applying a depth filter includes helically windingthe plurality of filaments over the oxygenator bundle to establish thefirst and second filter layers as each being composed of levelcross-wound filaments.
 24. The method of claim 23, wherein helicallywinding the plurality of hollow microporous fibers includes threading afiber guide of a winding apparatus with the hollow fibers and rotatingthe internal core relative to the fiber guide, and further whereinhelically winding the plurality of filaments includes: removing thehollow fibers from the fiber guide; threading at least some of thefilaments into the fiber guide; and rotating the internal core relativeto the fiber guide.
 25. The method of claim 22, wherein an outerdiameter of the filaments is less than an outer diameter of the fibers.26. The method of claim 22, wherein the filaments are solid.
 27. Themethod of claim 22, wherein the fibers are formed of a first materialand the filaments are formed of a second material differing from thefirst material.
 28. The method of claim 22, wherein a minimum gapspacing between axially adjacent filaments of the first filter layer isless than a minimum gap spacing between axially adjacent fibers of theoxygenator bundle.